5.11 Safety Function5-835 Operation5.11.2 External Device Monitor (EDM1)The external device monitor (EDM1) functions to monitor failures in the HWBB function. Connect the moni-tor to feedback signals to the safety function device.Note: To meet the performance level d (PLd) in EN ISO13849-1, the EDM signal must be monitored by a host controller.If the EDM signal is not monitored by a host controller, the system only qualifies for the performance level c (PLc). Failure Detection Signal for EDM1 SignalThe relation of the EDM1, /HWBB1, and /HWBB2 signals is shown below.Detection of failures in the EDM1 circuit can be checked using the following four status of the EDM1 signalin the table. Failures can be detected if the failure status can be confirmed, e.g., when the control power supplyis turned ON.(1) Connection Example and Specifications of EDM1 Output SignalConnection example and specifications of EDM1 output signal are explained below.SignalName Logic/HWBB1 ON ON OFF OFF/HWBB2 ON OFF ON OFFEDM1 OFF OFF OFF ONWARNING• The EDM1 signal is not a safety output. Use it only for monitoring a failure.For safety function signal connections, the input signal is the 0 V common and the outputsignal is the source output. This is opposite to other signals described in this manual. Toavoid confusion, the ON and OFF status of signals for safety functions are defined as fol-lows:ON: The state in which the relay contacts are closed or the transistor is ON and currentflows into the signal line.OFF: The state in which the relay contacts are open or the transistor is OFF and no cur-rent flows into the signal line.
